Medicaments for treating respiratory disorders are frequently administered as dry powder formulations through the mouth and nose. Dry powder medicament dispensers, such as inhalers, are used in the administration of these drugs, inhalation by the patient resulting in uptake of a specified dosage of medicament through the nose or mouth. The drug may be stored as a dry powder within a reservoir in the body of the inhaler, a metering chamber being utilised to administer a specified dose of medicament. Alternatively, more sophisticated medicament dispensers employ medicament carriers, such as individual capsules or blister packs/strips containing defined doses of powdered drug.
Patients often rely on medication delivered by dry powder inhalers for rapid treatment of respiratory disorders that are debilitating and in some cases life threatening. It is, therefore, essential that the prescribed dose of drug is delivered accurately and consistently to meet the patient's needs and comply with the requirements of regulatory authorities.
A problem which can occur in the storage and product lifetime of an inhaler is ingress of moisture into the medicament powder. A build-up of moisture can prevent the administration of an effective dose of medicament by causing an increase in particle size and/or adherence of hygroscopic particles to the walls of the carrier or device, thereby leading to reduced uptake via inhalation by the patient. In extreme cases, depending upon the chemical nature of the medicament, moisture build-up may lead to degradation of the drug.
Another problem can be microbial contamination, which is often assisted by the undesirable presence of excess moisture.
The Applicants have found that the inclusion of a desiccant in the body of the inhaler or the walls of the medicament carrier can significantly improve the aforementioned problems. Furthermore, storage of the inhaler or medicament carrier within a sealed is package incorporating a desiccant, can markedly reduce moisture ingress.
The Applicants has also found that the aforementioned problems can be ameliorated by controlling the ingress of moisture to, or egress of moisture from, the medicament container. Control may be achieved by either suitable choice of container materials or by enclosure of the container or a dispenser including the container in a suitable package. The control need not absolutely prevent moisture transfer. Indeed, the Applicants have found that under certain conditions a limited degree of moisture transfer can be desirable.
WO 99/32180 teaches the inclusion of moisture permeable chambers containing desiccants within a blister pack. U.S. Pat. No. 5,740,793 discloses the inclusion of a desiccant cartridge within an inhaler or the medicament carrier cassette. U.S. Pat. No. 5,394,868 describes a chamber within a powder inhaler for holding a desiccating substance. The use of desiccant filters within medicament dispensers is described in U.S. Pat. Nos. 5,687,746 and 5,775,320, and PCT patent application no. WO 89/01348.